The present invention relates to a sputtering target for use in the deposition of a granular-type magnetic thin film in a magnetic recording medium, and particularly relates to a Fe—Pt-based sputtering target in which C grains are dispersed.
In the field of magnetic recording as represented with a hard disk drive, a material based on Co, Fe or Ni, which are ferromagnetic metals, is used as a material of a magnetic thin film in the magnetic recording medium. For example, a Co—Cr-based or a Co—Cr—Pt-based ferromagnetic alloy having Co as its main component is being used for the magnetic thin film of a hard disk which adopts the longitudinal magnetic recording system.
Moreover, a compound material configured from a Co—Cr—Pt-based ferromagnetic alloy having Co as its main component and non-magnetic inorganic grains is often used for the magnetic thin film of a hard disk which adopts the perpendicular magnetic recording system that was recently put into practical application. In addition, the foregoing magnetic thin film is often produced by sputtering a target having the foregoing materials as its components with a DC magnetron sputtering device from the perspective of its high productivity.
Meanwhile, the recording density of hard disks is rapidly increasing year by year, and it is considered that the current surface density of 600 Gbit/in2 will reach 1 Tbit/in2 in the future. When the recording density reaches 1 Tbit/in2, the size of the recording bit will fall below 10 nm. In the foregoing case, it is anticipated that the superparamagnetism caused by thermal fluctuation will become a problem, and it is further anticipated that the currently used magnetic recording medium material; for instance, a material with increased crystal magnetic anisotropy obtained by adding Pt to a Co—Cr-based alloy, will become insufficient. This is because the magnetic grains that stably behave ferromagnetically when the size is 10 nm or less need to possess higher crystal magnetic anisotropy.
Due to the foregoing reason, a FePt phase having an L10 structure is attracting attention as a material for an ultrahigh-density recording medium. Since the L10 FePt phase has high crystal magnetic anisotropy and also yields superior corrosion resistance and oxidation resistance, it is expected to be a material that is suitable for application as a magnetic recording medium.
In addition, upon using the FePt phase as a material for use as an ultrahigh-density recording medium, demanded is the development of technology of dispersing the ordered FePt magnetic grains in a state where the FePt magnetic grains are magnetically isolated and the orientation of these grains is densely arranged as much as possible.
In light of the above, for a magnetic recording medium of the next-generation hard disk which adopts the thermal assist magnetic recording system, proposed is a magnetic thin film with granular structure in which the FePt magnetic grains having an L10 structure are isolated by a nonmagnetic material such as oxide or carbon. This magnetic thin film with granular structure has a structure where the magnetic grains are magnetically insulated from each other through the intervention of a non-magnetic substance.
As magnetic recording mediums having a magnetic thin film with granular structure and related publications thereof, there are Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5.
As a magnetic thin film with granular structure having the foregoing L10 FePt phase, a magnetic thin film containing C, as a non-magnetic substance, in a volume ratio of 10 to 50% is attracting attention particularly from the perspective of its high magnetic property. It is known that this kind of magnetic thin film with granular structure can be produced by simultaneously sputtering a Fe target, a Pt target, and a C target, or simultaneously sputtering a Fe—Pt alloy target and a C target. Nevertheless, an expensive simultaneous sputtering device is required for simultaneously sputtering the foregoing sputtering targets.
Moreover, when a sputtering device is used to sputter a sputtering target in which a nonmagnetic material is contained in an alloy, there is generally a problem in that the inadvertent desorption of the nonmagnetic material and abnormal discharge originating from the holes contained in the sputtering target will occur during sputtering, and particles (contaminant particles adhered onto the substrate) are consequently generated. In order to resolve the foregoing problems, it is necessary to increase the adhesion between the nonmagnetic material and the matrix alloy and highly densify the sputtering target. Generally speaking, a material of the sputtering target in which a nonmagnetic material is contained in an alloy is produced via the powder sintering method. However, when a large amount of C is included in Fe—Pt, it is difficult to obtain a high-density sintered compact since C is a sintering-resistant material.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2000-306228    [Patent Document 2] Japanese Laid-Open Patent Publication No. 2000-311329    [Patent Document 3] Japanese Laid-Open Patent Publication No. 2008-59733    [Patent Document 4] Japanese Laid-Open Patent Publication No. 2008-169464    [Patent Document 5] Japanese Laid-Open Patent Publication No. 2004-152471